CN117401697A - Lithium hexafluorophosphate and preparation process thereof - Google Patents
Lithium hexafluorophosphate and preparation process thereof Download PDFInfo
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- -1 Lithium hexafluorophosphate Chemical compound 0.000 title claims abstract description 65
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 claims abstract description 90
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 claims abstract description 50
- UHZYTMXLRWXGPK-UHFFFAOYSA-N phosphorus pentachloride Chemical compound ClP(Cl)(Cl)(Cl)Cl UHZYTMXLRWXGPK-UHFFFAOYSA-N 0.000 claims abstract description 31
- 238000000034 method Methods 0.000 claims abstract description 27
- 239000000203 mixture Substances 0.000 claims abstract description 27
- 239000003960 organic solvent Substances 0.000 claims abstract description 26
- 235000003270 potassium fluoride Nutrition 0.000 claims abstract description 25
- 239000011698 potassium fluoride Substances 0.000 claims abstract description 25
- 239000012025 fluorinating agent Substances 0.000 claims abstract description 20
- 239000003153 chemical reaction reagent Substances 0.000 claims abstract description 15
- 230000008569 process Effects 0.000 claims abstract description 14
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 claims abstract description 7
- 229910001634 calcium fluoride Inorganic materials 0.000 claims abstract description 7
- 238000004334 fluoridation Methods 0.000 claims abstract description 6
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical compound S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 claims abstract description 5
- VBKNTGMWIPUCRF-UHFFFAOYSA-M potassium;fluoride;hydrofluoride Chemical compound F.[F-].[K+] VBKNTGMWIPUCRF-UHFFFAOYSA-M 0.000 claims abstract description 5
- MIMUSZHMZBJBPO-UHFFFAOYSA-N 6-methoxy-8-nitroquinoline Chemical compound N1=CC=CC2=CC(OC)=CC([N+]([O-])=O)=C21 MIMUSZHMZBJBPO-UHFFFAOYSA-N 0.000 claims abstract description 3
- 238000006243 chemical reaction Methods 0.000 claims description 102
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 claims description 82
- 238000003682 fluorination reaction Methods 0.000 claims description 18
- 238000004519 manufacturing process Methods 0.000 claims description 12
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 claims description 9
- 230000035484 reaction time Effects 0.000 claims description 8
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 claims description 4
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 claims description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 claims description 3
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 claims description 3
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 claims description 2
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 claims description 2
- 239000002904 solvent Substances 0.000 abstract description 28
- 239000000243 solution Substances 0.000 description 58
- 238000001914 filtration Methods 0.000 description 32
- 238000001816 cooling Methods 0.000 description 30
- 238000003756 stirring Methods 0.000 description 28
- 239000000047 product Substances 0.000 description 26
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 18
- 239000002253 acid Substances 0.000 description 17
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 16
- 239000000706 filtrate Substances 0.000 description 16
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 16
- 239000013078 crystal Substances 0.000 description 15
- 238000001035 drying Methods 0.000 description 15
- 239000012065 filter cake Substances 0.000 description 15
- 238000002156 mixing Methods 0.000 description 15
- 238000005406 washing Methods 0.000 description 15
- 238000010438 heat treatment Methods 0.000 description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- 239000012295 chemical reaction liquid Substances 0.000 description 11
- 239000003792 electrolyte Substances 0.000 description 10
- OBCUTHMOOONNBS-UHFFFAOYSA-N phosphorus pentafluoride Chemical compound FP(F)(F)(F)F OBCUTHMOOONNBS-UHFFFAOYSA-N 0.000 description 10
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 7
- 229910001416 lithium ion Inorganic materials 0.000 description 7
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 description 6
- 229910013870 LiPF 6 Inorganic materials 0.000 description 5
- 239000000654 additive Substances 0.000 description 5
- 239000013067 intermediate product Substances 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- 230000000996 additive effect Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- 238000000746 purification Methods 0.000 description 4
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 3
- 238000005481 NMR spectroscopy Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000009776 industrial production Methods 0.000 description 3
- 239000001103 potassium chloride Substances 0.000 description 3
- 235000011164 potassium chloride Nutrition 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- 229910013872 LiPF Inorganic materials 0.000 description 2
- 101150058243 Lipf gene Proteins 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- FWZMWMSAGOVWEZ-UHFFFAOYSA-N potassium;hydrofluoride Chemical compound F.[K] FWZMWMSAGOVWEZ-UHFFFAOYSA-N 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- PNGLEYLFMHGIQO-UHFFFAOYSA-M sodium;3-(n-ethyl-3-methoxyanilino)-2-hydroxypropane-1-sulfonate;dihydrate Chemical compound O.O.[Na+].[O-]S(=O)(=O)CC(O)CN(CC)C1=CC=CC(OC)=C1 PNGLEYLFMHGIQO-UHFFFAOYSA-M 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229910018119 Li 3 PO 4 Inorganic materials 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000008280 blood Substances 0.000 description 1
- 210000004369 blood Anatomy 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000004210 ether based solvent Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 150000004673 fluoride salts Chemical class 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000035800 maturation Effects 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- RLOWWWKZYUNIDI-UHFFFAOYSA-N phosphinic chloride Chemical compound ClP=O RLOWWWKZYUNIDI-UHFFFAOYSA-N 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000007086 side reaction Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/005—Lithium hexafluorophosphate
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Secondary Cells (AREA)
Abstract
The invention belongs to the field of new energy, and discloses a preparation process of lithium hexafluorophosphate, which comprises the following steps: step 1: reacting lithium fluoride and phosphorus pentachloride in an organic solvent to obtain a first mixture; step 2: adding a fluorinating agent to the first mixture to obtain lithium hexafluorophosphate; the fluoridation reagent is one or more of potassium fluoride, ammonium fluoride, calcium fluoride, potassium bifluoride and ammonium bifluoride. The process can obtain lithium hexafluorophosphate by a solvent method, and the yield is not lower than 88%. Meanwhile, the invention also discloses lithium hexafluorophosphate obtained based on the process.
Description
Technical Field
The invention belongs to the field of new energy, and particularly relates to lithium hexafluorophosphate and a preparation process thereof.
Background
With the continuous advancement of new energy automobile industry as national development strategy, the demands of China on lithium ion batteries and related materials are continuously increased, and the demands on the performances of the lithium ion batteries are also continuously increased. The lithium ion battery mainly comprises an anode, a cathode, electrolyte and a diaphragm, wherein the electrolyte is transported between the anode and the cathode of the batteryAnd the role of conducting lithium ions, known as "blood" of lithium ion batteries. The purity of the electrolyte plays a vital role in the shelf time and service life, internal resistance and power characteristics, charge and discharge efficiency, service temperature range, safety performance and the like of the lithium ion battery. The most widely used electrolyte in lithium ion batteries is lithium hexafluorophosphate (LiPF) 6 ) The SEI film has the advantages of high conductivity, larger anion radius, difficult association, better electrochemical performance and the like, can form the SEI film on the surface of the electrode material, and can inhibit the corrosion of the current collector.
At present, the main current method for preparing lithium hexafluorophosphate at home and abroad is a hydrogen fluoride solvent method. For example: CN101570327A, CN114804060a et al report that lithium hexafluorophosphate is obtained by reacting anhydrous hydrogen fluoride with phosphorus pentachloride to produce a phosphorus pentafluoride mixed gas, and then introducing the phosphorus pentafluoride mixed gas into a hydrogen fluoride solution of lithium fluoride. CN101723346B, CN102951620a and the like react with phosphorus pentachloride and anhydrous hydrogen fluoride to obtain a mixed solution of hexafluorophosphoric acid and anhydrous hydrogen fluoride; preparing anhydrous hydrogen fluoride solution of lithium fluoride; and then adding the anhydrous hydrogen fluoride solution of lithium fluoride into the mixed solution of hexafluorophosphoric acid and anhydrous hydrogen fluoride to react to obtain the lithium hexafluorophosphate solution. CN104211029B, CN114865091a reports the preparation of lithium hexafluorophosphate solutions by adding phosphorus pentachloride directly to anhydrous hydrogen fluoride solution containing lithium fluoride.
On one hand, the hydrogen fluoride in the hydrogen fluoride solvent method is used as a solvent for dissolving lithium fluoride, so that the poor gas-solid and solid-solid reaction effects are avoided; on the other hand, the phosphorus pentachloride is fluorinated into phosphorus pentafluoride as a fluorinating agent, so that the direct use of the phosphorus pentafluoride with strong toxicity and corrosiveness as a raw material is avoided. Although the hydrogen fluoride solvent method has the above advantages, it has the following disadvantages: 1. the hydrogen fluoride is used as the raw material, so that the requirement on equipment is high, and potential safety hazards exist; 2. easy to generate LiPF 6 HF complexes, difficult to separate and purify, affecting product quality; 3. the production cost is high.
To avoid the use of hydrogen fluoride, the prior art also discloses a few solutions without hydrogen fluoride, such as:
CN1224405A discloses a method for preparing LiPF 6 LiF and P at normal pressureCl 5 Or POCl 3 Reaction at a reaction temperature of-20 to 300 ℃ for a reaction time of 0.1 to 10 hours to form LiPF 6 。
The reaction equation is:
a)PCl 5 +6LiF→5LiCl+LiPF 6
b)4POCl 3 +18LiF→12LiCl+Li 3 PO 4 +3LiPF 6 。
the patent also states that: "diethyl ether is preferably used as solvent, since LiPF6 is particularly easily dissolved in diethyl ether. As is clear from the data described in the examples of this patent, the yields were not more than 95% (specifically, 95.7%) when diethyl ether was used as the solvent, but not more than 90% when propylene carbonate (86.1%) and methylene chloride (83%) were used as the solvent. It is explained that this scheme requires very high solvent types, most suitably ether solvents, and that carbonate solvents, which are often used as electrolyte solvents, lead to reduced yields when used in this reaction. Although the use of diethyl ether in this scheme can achieve higher yields, there is also a patent (CN 1224405 a) that solvents such as diethyl ether tend to produce peroxides and that the impurities contained therein are complex, which reduces the quality of the product and increases the difficulty of purification.
The prior art also discloses schemes for preparing lithium hexafluorophosphate in pressurized environments, such as: CN103213963B discloses a method for directly preparing liquid lithium hexafluorophosphate (LiPF) 6 ) In the presence of a stabilizer and a catalyst, controlling the pressure to be 0.1-0.3Mpa, and directly preparing liquid lithium hexafluorophosphate by utilizing phosphorus pentachloride and lithium fluoride in a solvent. Although this method can produce lithium hexafluorophosphate in high yield, purification is also troublesome.
Thus, there is a need to find a process for preparing lithium hexafluorophosphate which can react at normal pressure, is convenient for purification, and has a yield that is not affected by the type of solvent.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a preparation process of lithium hexafluorophosphate, which can obtain lithium hexafluorophosphate by a solvent method under normal pressure, has the yield not influenced by the solvent type, and has simple post-treatment steps.
Meanwhile, the invention also discloses lithium hexafluorophosphate obtained based on the process.
In order to achieve the aim of the invention, the invention adopts the following technical scheme: a process for preparing lithium hexafluorophosphate, comprising the steps of:
step 1: reacting lithium fluoride and phosphorus pentachloride in an organic solvent to obtain a first mixture;
step 2: adding a fluorination reagent into the first mixture to react to obtain lithium hexafluorophosphate;
the fluoridation reagent is one or more of potassium fluoride, ammonium fluoride, calcium fluoride, potassium bifluoride and ammonium bifluoride.
Possible chemical reactions in step 1 are:
LiF+PCl 5 →LiPFCl 5
step 2 possible chemical reactions (for example potassium fluoride) are:
LiPFCl 5 +5KF→LiPF 6 +5KCl；
the principle of the reaction is as follows: the reaction is carried out by using a salt having a higher fluorination ability (such as potassium fluoride in the above equation) as a fluorinating agent, and the fluorinating agent is insoluble in an organic solvent in the reaction system. The solid-liquid reaction is carried out to obtain salt (such as potassium chloride in the above equation) without fluoridation capability, and the salt can be separated out from the solution, thus being convenient for separation.
Through the above process, the applicant has surprisingly found that the yield can be increased to 89% or more, more preferably to 95% or more, even more preferably to 98% or more.
The chloride in the final product of the invention exists in the solution in a form of precipitation, so unreacted fluoridation reagent and chloride can be removed by filtration, and the rest solution containing lithium hexafluorophosphate can be directly sold, thus obviously reducing the cost required by purification, precipitation and the like in the traditional method.
In the preparation process of the lithium hexafluorophosphate, the molar ratio of the lithium fluoride to the phosphorus pentachloride to the fluorinating agent is 1-7: 1:0.5 to 7.5.
Preferably, the molar ratio of the lithium fluoride, the phosphorus pentachloride and the fluorinating agent is 1.01-4: 1:2.5 to 6.5.
Generally, a ratio exceeding the above-mentioned ratio affects whether the reaction is completely performed or not, but does not affect whether the reaction is performed or not, such as excessive or insufficient amount of lithium fluoride, phosphorus pentachloride, only resulting in the remaining of a certain component; too little use of the fluorinating agent also results in that the fluorination cannot be completely performed to cause excessive impurities, while too much use of the fluorinating agent merely results in serious redundancy and waste of the fluorinating agent. The above ratio ranges are preferable for industrial production.
In some embodiments of the invention, the molar ratio of lithium fluoride to phosphorus pentachloride may be 1.01: 1. 1.5: 1. 1.03: 1. 2: 1. 3: 1. 4: 1.5: 1. 6: 1. 6.5:1 or 7:1, a step of;
in some embodiments of the invention, the molar ratio of phosphorus pentachloride to fluorinating agent is 1:5.1, 1:5.5, 1:6. 1:6.5, 1:7 or 1:7.5.
in the preparation process of the lithium hexafluorophosphate, the mass ratio of the organic solvent to the lithium fluoride is 20-30: 1. in the step 1, the organic solvent is not too much, and the excessive organic solvent is not favorable for the rapid conversion in the first step;
in some embodiments of the invention, the mass ratio of the organic solvent to lithium fluoride is 20: 1. 21: 1. 22: 1. 23: 1. 24: 1. 25: 1. 26: 1. 27: 1. 28: 1. 29:1 or 30:1, a step of;
in the preparation process of the lithium hexafluorophosphate, the step 1 is carried out at normal temperature and normal pressure for 2-4 hours. In some embodiments of the invention, the reaction time is 2 hours, 3 hours, or 4 hours; the normal temperature refers to the normal temperature which does not need specific control of the reaction temperature, for example, the reaction temperature can be 10-40 ℃, and the reaction temperature can be 10 ℃, 20 ℃, 25 ℃, 30 ℃ and 40 ℃ alternatively;
it should be noted that the present invention does not exclude that the reaction is performed at a higher temperature and a higher pressure, and that the reaction can be performed at normal temperature and normal pressure, and that the operation under pressure is generally possible, for example, the pressure is 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa or 0.5MPa; the reaction temperature can be controlled in a higher temperature range such as 40 ℃, 50 ℃, 60 ℃, 70 ℃ or 80 ℃;
in the preparation process of the lithium hexafluorophosphate, the reaction temperature in the step 2 is 70-100 ℃ and the reaction time is 6-10 h. The fluorinating agent is added to the first mixture along with the organic solvent in the step 2; the weight of the organic solvent used in the step 2 is 2.5-5 times of the weight of the fluorinating agent.
In the course of practical experiments, we found that under too low a temperature, incomplete fluorination and too high a temperature, not only excessive energy consumption and boiling of the solvent, but also unexpected side reactions may occur, and based on the choice of the maturation process, the reaction was suggested to be carried out in the above temperature range.
In some embodiments of the invention, the reaction time is short and does not allow for the synthesis of the lithium hexafluorophosphate of the invention, but the preferred reaction time allows for as high a yield of lithium hexafluorophosphate as possible; in some embodiments of the invention, the reaction time is 6h, 7h, 8h, 9h, or 10h;
in the preparation process of lithium hexafluorophosphate, the organic solvent is one or more of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, ethylene carbonate and propylene carbonate.
The present invention is not limited to the above organic solvents, such as diethyl ether or other organic solvents described in the prior art, which can give the products of the present invention, but the present invention is not selected for use in practical industrial production based on the insufficiently stable nature of these solvents themselves; it is not excluded that the organic solvent of the present invention may comprise a non-preferred organic solvent as above.
At the same time, the final product according to the invention is sold in solution, so that, in general, it is recommended to select the combination with the solvent required by the customer for the battery product of the customer.
Based on the above analysis, in the process control of the present invention, the ratio of substances, the kind and amount of solvents, the reaction temperature and time, etc., can be well obtained within reasonable ranges that can be expected by those skilled in the art, and will not affect the decision of whether the reaction can be performed.
Optimization, modification and combination of process parameters performed with respect to the present invention should be considered within the scope of the present invention.
Finally, the invention also discloses lithium hexafluorophosphate obtained by adopting any one of the preparation processes.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention does not use anhydrous hydrogen fluoride, and has simple operation, high safety and high yield;
(2) The electrolyte is used as a common organic solvent, so that lithium hexafluorophosphate liquid salt can be directly obtained for sale;
(3) The phosphorus pentafluoride is not used as a raw material, the phosphorus pentafluoride is not required to be prepared, the potential safety hazard is reduced, and meanwhile, the influence of the impurity of the phosphorus pentafluoride on the quality of lithium hexafluorophosphate is avoided;
(4) Can react under normal pressure, has low requirements on reaction equipment, and simultaneously saves energy consumption;
(5) The solvent type has no critical influence on the yield, and the common solvents can realize high yield;
(6) The product is easy to separate and purify, has high quality and is suitable for industrial production.
The principle is as follows: under the conditions of normal temperature and normal pressure, the lithium fluoride and the phosphorus pentafluoride can only carry out the chemical reaction shown in the step 1 relatively quickly, and the lithium fluoride is intended to further fluoride LiPFCl 5 Obtaining lithium hexafluorophosphate requires longer time, greater pressure or under catalytic conditions (e.g., CN 103213963B). Especially in the case of low raw material concentration in the late stage of the reaction, from LiPFCl 5 The reaction to lithium hexafluorophosphate takes more time and is more difficult to react thoroughly. The method promotes the forward progress of the fluorination reaction by utilizing the fluorination reagent with stronger fluorination capability than lithium fluoride in the step 2, thereby shortening the reaction time and avoiding harsh reaction conditions so as to lead the reaction to be carried outHigher yields are achieved with shorter times.
Drawings
FIG. 1 is a nuclear magnetic resonance (F-NMR) spectrum of the product of example 1;
FIG. 2 is a nuclear magnetic resonance (P-NMR) spectrum of the product of example 1.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
(1) 524g of methyl ethyl carbonate, 26.2g (1.01 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 2 hours to obtain a first reaction liquid;
(2) Adding methyl ethyl carbonate solution dispersed with potassium fluoride into the first reaction solution, wherein the total weight of the methyl ethyl carbonate solution is 1200g, the methyl ethyl carbonate solution contains 319g (5.5 mol) of potassium fluoride, stirring and heating to 70 ℃, and preserving heat for reaction for 9h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain lithium hexafluorophosphate product (the sample is sent for inspection, the nuclear magnetic pattern can be seen in fig. 1 and 2), the yield is 98.5%, the purity is 99.95%, the water content is 18ppm, and the free acid content is 72ppm.
Example 2
(1) 688g of methyl ethyl carbonate, 27.5g (1.06 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 3 hours to obtain a first reaction liquid;
(2) Adding a methyl ethyl carbonate solution in which potassium fluoride is dispersed into the first reaction solution, wherein the total weight of the methyl ethyl carbonate solution is 1400g, and the methyl ethyl carbonate solution contains 377.5g (6.5 mol) of potassium fluoride, stirring and heating to 85 ℃, and preserving heat for reaction for 8 hours;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 98.6%, the purity of 99.97%, the water content of 16ppm and the free acid content of 68ppm.
Example 3
(1) 855g of methyl ethyl carbonate, 28.5g (1.1 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 4 hours to obtain a first reaction liquid;
(2) Adding methyl ethyl carbonate solution dispersed with potassium fluoride into the first reaction solution, wherein the total weight of the methyl ethyl carbonate solution is 1600g, 435g (7.5 mol) of potassium fluoride is contained, stirring and heating to 100 ℃, and preserving heat for reaction for 6h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 98.8%, the purity of 99.97%, the water content of 12ppm and the free acid content of 66ppm.
Example 4
(1) 688g of methyl ethyl carbonate, 27.5g (1.06 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 3 hours to obtain a first reaction liquid;
(2) Adding an ethyl methyl carbonate solution in which ammonium fluoride is dispersed into the first reaction solution, wherein the total weight of the ethyl methyl carbonate solution is 1000g, and the ethyl methyl carbonate solution contains 203g (5.5 mol) of ammonium fluoride, stirring and heating to 80 ℃, and preserving heat for reaction for 8 hours;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain a lithium hexafluorophosphate product with the yield of 98.5%, the purity of 99.96%, the moisture content of 17ppm and the free acid content of 70ppm.
Example 5
(1) 650g of methyl ethyl carbonate, 27.5g (1.06 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 3 hours to obtain a first reaction liquid;
(2) Adding a methyl ethyl carbonate solution with calcium fluoride dispersed therein into the first reaction solution, wherein the total weight of the methyl ethyl carbonate solution is 1800g, the solution contains 430g (5.5 mol) of calcium fluoride, stirring and heating to 80 ℃, and preserving heat for reaction for 8h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 98.8%, the purity of 99.98%, the water content of 15ppm and the free acid content of 64ppm.
Example 6
(1) 700g of methyl ethyl carbonate, 27.5g (1.06 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 3 hours to obtain a first reaction solution;
(2) Adding methyl ethyl carbonate solution dispersed with potassium bifluoride into the first reaction liquid, wherein the total weight of the methyl ethyl carbonate solution is 2000g, 547g (7 mol) of potassium bifluoride is contained, stirring and heating to 80 ℃, and preserving heat for reaction for 8h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 98.8%, the purity of 99.97%, the water content of 16ppm and the free acid content of 68ppm.
Example 7
Substantially the same as in example 1, the difference is that: the fluorinating agent adopts a mixture of potassium fluoride and potassium fluorohydride, the total molar amount of which is 5.5mol, and the molar ratio of the potassium fluoride to the potassium fluorohydride is 1:1.
After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 98.2%, the purity of 99.95%, the moisture content of 17ppm and the free acid content of 63ppm.
Example 8
Substantially the same as in example 1, the difference is that: the fluoridation reagent adopts a mixture of potassium fluoride and calcium fluoride, the total molar quantity is 5.5mol, and the molar ratio of the potassium fluoride to the calcium fluoride is 1:1.
After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 98.7%, the purity of 99.94%, the water content of 20ppm and the free acid content of 78ppm.
Example 9
Substantially as in example 1, except that the organic solvent was replaced with dimethyl carbonate by methyl ethyl carbonate.
The reaction results are: yield 98.9%, purity 99.96%, moisture 14ppm, free acid 53ppm.
Example 10
Substantially as in example 1, except that the organic solvent was replaced with diethyl carbonate by methylethyl carbonate.
The reaction results are: yield 98.5%, purity 99.97%, moisture 19ppm, free acid 57ppm.
In the process of carrying out the project, the common solvents of methyl peracetate, ethyl acetate, ethylene carbonate and propylene carbonate are independently used to replace methyl ethyl carbonate, the experimental results are similar to those of the case of adopting similar process parameters and adopting methyl ethyl carbonate as the solvent, and the yield of not less than 95% is generally found, and the combination of the solvents can also obtain satisfactory yield.
Example 11
(1) 724g of methyl ethyl carbonate, 52.4g (2 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 2 hours to obtain a first reaction liquid;
(2) Adding a methyl ethyl carbonate solution in which potassium fluoride is dispersed into the first reaction solution, wherein the total weight of the methyl ethyl carbonate solution is 1000g, 261.6g (4.51 mol) of potassium fluoride is contained, stirring and heating to 70 ℃, and preserving heat for reaction for 9h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 96.4%, the purity of 99.91%, the water content of 14ppm and the free acid content of 71ppm.
Example 12
(1) 824g of methyl ethyl carbonate, 78.6g (3 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 2 hours to obtain a first reaction solution;
(2) Adding a methyl ethyl carbonate solution in which potassium fluoride is dispersed into the first reaction solution, wherein the total weight of the methyl ethyl carbonate solution is 900g, and the methyl ethyl carbonate solution contains 203.6g (3.51 mol) of potassium fluoride, stirring and heating to 70 ℃, and preserving heat for reaction for 9h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 94.1%, the purity of 99.92%, the water content of 21ppm and the free acid content of 79ppm.
Example 13
(1) 924g of methyl ethyl carbonate, 104.8g (4 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 2 hours to obtain a first reaction liquid;
(2) Adding an ethyl methyl carbonate solution dispersed with potassium fluoride into the first reaction solution, wherein the total weight of the ethyl methyl carbonate solution is 800g, and the ethyl methyl carbonate solution contains 145.6g (2.51 mol) of potassium fluoride, stirring and heating to 70 ℃, and preserving heat for reaction for 9h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 91.6%, the purity of 99.87%, the water content of 25ppm and the free acid of 67ppm.
Example 14
(1) 1024g of methyl ethyl carbonate, 131g (5 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 2 hours to obtain a first reaction solution;
(2) Adding methyl ethyl carbonate solution dispersed with potassium fluoride into the first reaction solution, wherein the total weight of the methyl ethyl carbonate solution is 700g, and the methyl ethyl carbonate solution contains 87.6g (1.5 mol) of potassium fluoride, stirring and heating to 70 ℃, and preserving heat for reaction for 9h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 89.5%, the purity of 99.89%, the water content of 23ppm and the free acid content of 71ppm.
Example 15
(1) 1224g of methyl ethyl carbonate, 157.2g (6 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 2 hours to obtain a first reaction liquid;
(2) Adding methyl ethyl carbonate solution dispersed with potassium fluoride into the first reaction solution, wherein the total weight of the methyl ethyl carbonate solution is 500g, the methyl ethyl carbonate solution contains 29.6g (0.51 mol) of potassium fluoride, stirring and heating to 70 ℃, and preserving heat for reaction for 9h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 88.1%, the purity of 99.91%, the water content of 22ppm and the free acid content of 73ppm.
Example 16
Substantially as in example 1, except that: in the step 3, the reaction is finished, the temperature is reduced to room temperature, the mixture is stood and filtered, and the mixture is washed three times with 30g of methyl ethyl carbonate each time; and combining the filtrates to complete the whole reaction process.
The electrolyte of this example was diluted or concentrated according to the customer's needs so that the content of lithium hexafluorophosphate was adjusted in the range of 8 to 25 wt%.
It should be noted that the operations performed in example 16 can still be applied to examples 1 to 15; in the actual production and sales process, according to different demands of customers, organic solvents required by customers are selected as a reaction continuous phase in the step 1 and the step 2;
as a common commercial formulation of the electrolyte, various types of additives such as an additive for improving the high temperature resistance of the electrolyte/battery, an additive for improving the low temperature resistance of the electrolyte/battery, an additive for improving the cycle performance of the battery, an additive for reducing the impedance of the battery, and the like may also be added on the basis of the above-described embodiments before shipment.
Comparative example 1
(1) 1724g of methyl ethyl carbonate, 169.3g (6.51 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 2 hours to obtain a first reaction liquid;
(2) Stirring and heating to 70 ℃, and preserving heat and reacting for 9h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 84.3%, the purity of 99.91%, the water content of 19ppm and the free acid content of 75ppm.
Comparative example 2
(1) 524g of methyl ethyl carbonate, 26.2g (1.01 mol) of lithium fluoride and 208.2g (1 mol) of phosphorus pentachloride are added into a dry reaction kettle at room temperature, and the mixture is stirred and reacted for 2 hours to obtain a first reaction liquid;
(2) Adding methyl ethyl carbonate solution in which lithium fluoride is dispersed into the first reaction solution, wherein the total weight of the methyl ethyl carbonate solution is 1200g, and the methyl ethyl carbonate solution contains 143g (5.5 mol) of lithium fluoride, stirring and heating to 70 ℃, and preserving heat for reaction for 9h;
(3) After the reaction, cooling to room temperature, standing, filtering and washing with ethyl methyl carbonate for three times, wherein 30g of ethyl methyl carbonate is used for each time; mixing the filtrates, concentrating under reduced pressure until crystals are separated out, stopping concentrating, cooling to 0-5deg.C, stirring, and crystallizing for 1 hr; filtering, and drying the filter cake to obtain the lithium hexafluorophosphate product with the yield of 87.6%, the purity of 99.91%, the water content of 20ppm and the free acid content of 70ppm.
It should be noted that: the conversion of all examples and comparative examples of the present invention was calculated on the basis of phosphorus pentachloride.
Analysis of results:
1. it can be seen from examples 1 to 6 that the process according to the present application allows higher yields to be achieved under different process parameters.
The invention has the other characteristic that the fluoride salt can be directly filtered and separated, and the mixture of the rest lithium hexafluorophosphate and the organic solvent can be directly sold without treatment, thereby effectively reducing the production cost. The reason is that: in an organic solvent system, salts such as potassium chloride and the like are easier to separate out in the organic system than lithium chloride; therefore, products such as potassium chloride and the like generated by the reaction can be basically removed through filtration, and the lithium hexafluorophosphate with high purity is obtained.
2. The inventors have also made a number of experiments replacing different solvents, and have found that the solvent type does not have a decisive influence on the final yield.
3. The use of specific fluorinating agents is the basis for the realization of the present invention, as can be seen by comparison of examples 1 and 2, high yields cannot be obtained in common solvent systems using processes similar to the prior art.
Compared with comparative examples 1 and 2 (traditional technology), the yield is improved by 10-15%, the separation difficulty of the product can be reduced, and the purity of the product can be improved.
The possible reasons are: in the reaction process of lithium fluoride and phosphorus pentafluoride, lithium fluoride can be used as a fluorination reagent to fluorinate an intermediate product, and finally lithium hexafluorophosphate is obtained. However, since the fluorination ability of lithium fluoride is relatively general, in the latter stage of the reaction, the concentration of lithium fluoride and phosphorus pentafluoride or an intermediate product is low, and the reaction rate is remarkably slow without special treatment such as pressurization or addition of a catalyst, and it is difficult to obtain a high yield in a short time. The intermediate product of the step 1 is formed at a higher speed, and after the intermediate product is quickly generated, other fluorination reagents with higher fluorination capacity are adopted to fluorinate the intermediate product, so that the efficiency of the fluorination reaction of the step 2 is improved, and the effect of short-time high yield of the whole reaction is ensured.
4. It can be seen from examples 1, 11 to 15 that the yield of lithium hexafluorophosphate in the product gradually increases with increasing amount of the fluorination reagent in step 2 under the condition that the total amount of lithium fluoride and the fluorination reagent is unchanged. This illustrates: the addition of the fluorination reagent selected in step 2 can accelerate the reaction, and the more the amount of the fluorination reagent is in a certain range, the more obvious the conversion rate improvement effect is. Referring to examples 14 and 15, the conversion rate improving ability was weak because the reaction of step 2 was only performed to some extent due to the smaller amount of the fluorinating agent compared to the case of more lithium fluoride and phosphorus pentachloride, and the reaction of lithium fluoride and phosphorus pentachloride was still the main stream in the reaction system.
Therefore, the choice of suitable fluorinating agent and timing of addition of the fluorinating agent is critical and central to the present application in order to achieve high yields in common organic solvent systems.
The applicant states that the process of the invention is illustrated by the above examples, but the invention is not limited to the above process steps, which do not mean that the invention must be carried out in dependence on the above process steps. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of selected raw materials, addition of auxiliary components, selection of specific modes, etc. fall within the scope of the present invention and the scope of disclosure.
Claims (9)
1. The preparation process of the lithium hexafluorophosphate is characterized by comprising the following steps of:
step 1: reacting lithium fluoride and phosphorus pentachloride in an organic solvent to obtain a first mixture;
step 2: adding a fluorination reagent into the first mixture to react to obtain lithium hexafluorophosphate;
the fluoridation reagent is one or more of potassium fluoride, ammonium fluoride, calcium fluoride, potassium bifluoride and ammonium bifluoride.
2. The process for preparing lithium hexafluorophosphate according to claim 1, wherein the molar ratio of lithium fluoride, phosphorus pentachloride and fluorinating agent is 1 to 7:1:0.5 to 7.5.
3. The process for preparing lithium hexafluorophosphate according to claim 1, wherein the molar ratio of lithium fluoride, phosphorus pentachloride and fluorinating agent is 1.01 to 4:1:2.5 to 6.5.
4. The process for preparing lithium hexafluorophosphate according to claim 1, wherein the mass ratio of the organic solvent to the lithium fluoride in the step 1 is 20-30: 1.
5. the process for preparing lithium hexafluorophosphate according to claim 1, wherein the step 1 is carried out at normal temperature and pressure for 2-4 hours.
6. The process for preparing lithium hexafluorophosphate according to claim 1, wherein the reaction temperature in the step 2 is 70-100 ℃ and the reaction time is 6-10 h.
7. The process for preparing lithium hexafluorophosphate according to claim 1, wherein the fluorination reagent in step 2 is added to the first mixture along with the organic solvent; the weight of the organic solvent used in the step 2 is 2.5-5 times of the weight of the fluorinating agent.
8. The process for preparing lithium hexafluorophosphate according to claim 1, wherein the organic solvent is one or more of dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, ethylene carbonate and propylene carbonate.
9. Lithium hexafluorophosphate obtained by the process according to any one of claims 1 to 8.
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